The present invention relates to a catheter adapted to be inserted into a narrow region, such as a duct of a living body, and used to perform medical operations, such as injection of a contrast medium, recovery of foreign substances, extraction of cells, ablation of affected parts, insertion of a guide wire, etc.
A catheter that is inserted into a duct of a living body or the like, in order to perform medical operations, such as injection of a contrast medium, recovery of foreign substances, extraction of cells, ablation of affected parts, insertion of a guide wire, etc., generally comprises a flexible elongate insert section and an operating section on the hand side. The distal end side of the insert section can be bent so that the distal end of the insert section is directed toward a desired region in the living body. More specifically, the distal end side of the insert section can be bent by pushing or pulling an operating wire, which is fixedly connected to the distal end portion of the insert section, by means of the operating section on the hand side.
Operation for guiding the catheter into a narrow region deep in the living body is very difficult and requires considerable skill. FIG. 12 shows the way a catheter 102 is guided through the channel of an endoscope 100 to a region near a duodenal papilla 105, and an operative instrument 104 is inserted into a bile duct 106 through the opening of the duodenal papilla 105 by means of the catheter 102 that projects from the channel of the endoscope 100. In this operation, the operative instrument 104 that is inserted in a lumen of the catheter 102, cannot be inserted through the duodenal papilla 105 into the bile duct 106 unless the distal end side of an insert section 102a of the catheter 102 is bent to a given degree in a given direction such that the distal end of the insert section 102a can be exactly directed toward the opening of the duodenal papilla 105.
Conventionally, various attempts have been made to direct the distal end of a catheter toward a desired region of a living body. Described in Jpn. Pat. Appln. KOKAI Publication No. 5-38342, for example, is a technique in which the distal end side of the insert section 102a of the catheter 102 is provided with a plurality of notches 103 that are eccentric to the axis of the insert section 102a so that it easily bends to the side on which the notches 103 are located, as shown in FIG. 12, whereby the insert section 102 can be readily directed toward the target region.
If the insert section 102a is provided with the notches 103 that are eccentric to its axis, as described in Jpn. Pat. Appln. KOKAI Publication No. 5-38342, the bending direction of the insert section 102a can no doubt be regulated to some degree. However, this alone cannot be said to be a radical solution.
In order to guide the catheter 102 to the duodenal papilla 105, the flexible elongate insert section 102a of the catheter 102 is first inserted into the channel of the winding insert section of the endoscope 100 in the living body, and the distal end side of the insert section 102a is caused to project from the distal end of the insert section of the endoscope 100. Thereafter, the projected distal end side of the insert section 102a is bent and directed toward the duodenal papilla. The key factor in this operation is to protrude the insert section 102a of the catheter 102 from the distal end of the insert section of the endoscope 100 with that side of the insert section 102a for the notches 103 directed toward the duodenal papilla 105 (upper side of the drawing), and thereafter, the distal end side of the insert section 102a is bent to a desired degree without failing to maintain this direction of protrusion.
However, the insert section 102a of the catheter 102 may be inserted in any direction into the channel of the endoscope 100. Thus, if the catheter 102 is oriented when the catheter 102 starts to be inserted into the channel of the endoscope 100, the catheter 102 may be redirected by its own rotation or the like in the channel of the endoscope 100 as the catheter 102 passes through the channel of the endoscope 100 that winds intricately in the living body. Consequently, the catheter 102 may fail to be caused to project from the endoscope 100 with that side of the insert section 102a for the notches 103 directed toward the duodenal papilla 105, in some cases.
Even in the case where the catheter 102 can be caused to project from the endoscope 100 with that side for the notches 103 directed toward the duodenal papilla 105, moreover, the distal end of the catheter 102 cannot be directed successfully toward the duodenal papilla 105 unless the catheter 102 is bent without changing the direction of its projection. If the distal end portion of the catheter 102 is provided with the notches 103, in particular, the stiffness of the region with the notches 103 lowers, making it hard to steadily maintain the direction of projection of the catheter 102.
Since the catheter is elongate and flexible, the catheter inevitably meanders as the distal end side of the insert section of the catheter 102 is bent by pushing or pulling the operating wire. In some cases, therefore, a stroke on the hand side cannot be transmitted successfully to the distal end side, meaning that a desired curvature cannot be obtained. If the distal end side of the insert section 102a cannot be bent to a necessary degree, the distal end of the catheter 102 cannot be directed successfully toward the duodenal papilla 105.
Thus, if the catheter 102 cannot be caused to project from the endoscope with the specially provided notches 103 directed toward the duodenal papilla 105, it is hard to direct the distal end of the catheter 102 toward the duodenal papilla 105, in consequence. If the catheter 102 can be caused to project from the endoscope 100 with the notches 103 directed toward the duodenal papilla 105, moreover, the distal end side of the catheter 102 cannot be bent to a desired degree in a desired direction unless a handling force on the hand side can be efficiently accurately transmitted to the distal end side without failing to maintain the direction of its projection. Thus, the distal end of the insert section 102a cannot be directed toward the duodenal papilla 105 exactly and speedily.